Anodizing apparatus

ABSTRACT

An anodizing apparatus includes a first electrode member electrically connected to a processing subject formed with a circumferential groove at an outer circumferential surface thereof, a second electrode member including an inner circumferential surface, facing each of the outer circumferential surface and the circumferential groove of so as to include an interval, elastic seal members for sealing a clearance generated between the outer circumferential surface of and the inner circumferential surface, and a thrusting mechanism thrusting the elastic seal members to the second electrode member, and thereby elastically deforming the elastic seal members so as to seal the clearance. The thrusting mechanism is switchable between a thrusting state and a released state. A fluid supplying passage, through which an electrolytic solution is supplied to the circumferential groove, and a fluid discharging passage, through which the electrolytic solution is discharged, are formed so as to open at the inner circumferential surface.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 U.S.C. §119 to Japanese Patent Application 2009-008720, filed on Jan. 19, 2009, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to an anodizing apparatus.

BACKGROUND DISCUSSION

According to the anodizing apparatus, disclosed in JP2003-113496A, an acid electrolytic solution including sulfuric acid, chromic acid and the like, is used. Further, the first electrode member is electrically connected to the processing subject so that the processing subject serves as an anode. The processing subject and the second electrode member are energized through the electrolytic solution. Consequently, a surface of the processing subject, which is made of, for example, an aluminum-based metal, is oxidized, and thereby an alumite coating is formed. According to the anodizing apparatus, disclosed in JP2003-113496A, a stick-shaped second electrode member is immersed in the electrolytic solution.

According to the known anodizing apparatus, however, since the stick-shaped second electrode member is immersed in the electrolytic solution, an electric current may concentrate at a portion of the circumferential groove of the processing subject in the vicinity of the second electrode member. Therefore, it may be difficult to uniform density of an electric current along the circumferential groove of the processing subject. Accordingly, forming a coating whose thickness is even along a longitudinal direction of the circumferential groove of the processing subject, may be difficult.

A need thus exists for an anodizing apparatus that is not susceptible to the drawback mentioned above.

SUMMARY

According to an aspect of this disclosure, an anodizing apparatus includes a first electrode member electrically connected to a processing subject, made of metal and formed with a circumferential groove at an outer circumferential surface thereof, a second electrode member including an inner circumferential surface, formed into an annular shape and facing each of the outer circumferential surface of the processing subject and the circumferential groove of the processing subject so as to include an interval between the second electrode member and each of the outer circumferential surface of the processing subject and the circumferential groove of the processing subject, elastic seal members being nonconductive, respectively formed into an annular shape, and respectively provided at both sides of the circumferential groove in a width direction thereof for sealing a clearance generated between the outer circumferential surface of the processing subject and the inner circumferential surface of the second electrode member, and a thrusting mechanism thrusting each of the elastic seal members relative to the second electrode member in the width direction of the circumferential groove of the processing subject, and thereby elastically deforming each of the elastic seal members so as to seal the clearance. The thrusting mechanism is switchable between a thrusting state for thrusting the elastic seal members and a released state for releasing the thrusting of the elastic seal members. A fluid supplying passage, through which an electrolytic solution is supplied to the circumferential groove of the processing subject, and a fluid discharging passage, through which the electrolytic solution, supplied to the circumferential groove of the processing subject, is discharged, are formed so as to open at the inner circumferential surface of the second electrode member.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with the reference to the accompanying drawings, wherein:

FIG. 1 is a schematic view illustrating an anodizing apparatus;

FIG. 2A is a side view illustrating a main portion of the anodizing apparatus;

FIG. 2B is an enlarged side view illustrating the main portion of the anodizing apparatus;

FIG. 3A is a side view illustrating the main portion of the anodizing apparatus;

FIG. 3B is an enlarged side view illustrating the main portion of the anodizing apparatus; and

FIG. 4 is a planar view illustrating the main portion of the anodizing apparatus.

DETAILED DESCRIPTION

An embodiment of an anodizing apparatus will be explained hereinafter with reference to the attached drawings. Directions, such as upper, lower, vertical, horizontal and the like mentioned hereinafter correspond to an orientation of the anodizing apparatus. FIG. 1 illustrates the anodizing apparatus for anodizing a first piston ring groove A1 of a metal-made processing subject, such as of a piston A, made of an aluminum alloy, for example.

More specifically, the first piston ring groove A1, a second piston ring groove A2 and a third piston ring groove A3 are formed at the piston A so as to be aligned from an lower end portion of the piston A toward a skirt portion thereof. The anodizing apparatus according to the embodiment anodizes an outer circumferential surface of the piston A, including the first piston ring (a compression ring) groove A1, which is provided closest to the lower end portion of the piston A among the first, second and third piston ring grooves A1, A2 and A3. The first piston ring groove A1, formed at a first outer circumferential surface 22 of the piston (a processing subject) A, serves as a circumferential groove.

The anodizing apparatus includes an electrolytic solution tank 1, an electrolytic solution supplying portion 2, an oxidizing portion 3 and an energizing portion 4.

The electrolytic solution container 1, made of vinyl chloride or SUS 316, is formed into a container shape whose upper end is open. The electrolytic solution container 1 includes a recycle passage 5 for receiving and collecting an electrolytic solution, which has flown through the oxidizing portion 3 and for recycling the electrolytic solution to the electrolytic solution supplying portion 2.

The electrolytic solution supplying portion 2 includes a cooling container 6, a supplying passage 7, a supplying pump 8 and a supplying control portion 9. The cooling container 6 is provided for cooling the electrolytic solution, which is recycled from the electrolytic solution container 1. The supplying passage 7 is used for supplying the electrolytic solution from the cooling container 6 to the oxidizing portion 3. The supplying pump 8 is provided at the supplying passage 7. The supplying control portion 9 controls an operation of the supplying pump 8 so that the electrolytic solution is supplied to the oxidizing portion 3 at a predetermined timing.

The cooling container 6 includes a cooling device 10, a temperature sensor 11 and a cooling control portion 12. The cooling device 10 cools the electrolytic solution, which is collected from the oxidizing portion 3. The cooling control portion 12 controls an operation of the cooling device 10 based on information of a temperature of the electrolytic solution, detected by means of the temperature sensor 11, so that the electrolytic solution is cooled to a predetermined temperature.

The energizing portion 4 energizes the oxidizing portion 3. The energizing portion 4 may include an electric current control means for adjusting electric current density. A known electric current control means, including an ammeter, a voltmeter, a commutator and the like, may be used.

As illustrated in FIGS. 2 and 3, the oxidizing portion 3 includes a first electrode (anode) portion 13 and a second electrode (cathode) portion 14. The first electrode portion 13 includes a first electrode member 15 and a lifting and lowering device 16. The first electrode member 15 is made of metal, such as copper, SUS 316 or the like, which are electrically conductive. The lifting and lowering device 16 lifts and lowers the first electrode member 15 relative to the second electrode portion 14. Further, the first electrode member 15 also serves as a holding means for holding the piston A. The first electrode member 15 is electrically connected to an anode terminal 4 a of the energizing portion 4.

The first electrode member (the holding means) 15 includes an engagement portion, which is engageable with/disengageable from an inner circumferential surface of the piston A, at a lower end portion thereof. The first electrode member 15 engages with the piston A by means of the engagement portion, thereby holding the piston A so that an axis of the piston A extends along a vertical direction in a state where the first electrode member 15 and the piston A are electrically connected.

The second electrode portion 14 includes a second electrode member 17, a movable plate 18 and a fixed plate 19. The second electrode member 17 is made of metal, such as copper, SUS 316, or the like, which are electrically conductive. The movable plate 18 and the fixed plate 19, each of which is made of nonconductive material (insulator), such as vinyl chloride resin or the like, are arranged at upper and lower portions of the second electrode member 17, respectively.

As illustrated in FIGS. 3 and 4, the second electrode member 17 is formed with a piston insertion hole 20 for inserting the piston A therein, in a state where the axis of the piston A extends in an upper-lower direction. Consequently, the second electrode member 17 is formed into a substantially annular shape having a rectangular-shaped cross section. The second electrode member 17 is electrically connected to a cathode 4 b of the energizing portion 4.

An inner circumferential surface 21, which forms the piston insertion hole 20, faces the first outer circumferential surface 22 of the piston A and the first piston ring groove A1 for an entire circumference so as to include a predetermined interval therebetween, and thereby the inner circumferential surface 21 is formed into a substantially annular shape.

As illustrated in FIG. 4, each of a plurality of fluid supplying passages 23 and each of a plurality of fluid discharging passages 24 are alternately formed so as to open at the inner circumferential surface 21, which forms the piston insertion hole 20, so as to include an interval between the adjacent passages. The plurality of fluid supplying passages 23 is used for supplying the electrolytic solution to the first piston ring groove A1. The plurality of fluid discharging passages 24 is used for discharging the electrolytic solution, which is supplied to the first piston ring groove A1. Each of the plurality of the fluid supplying passages 23 and each of the plurality of the fluid discharging passages 24 is arranged so as to extend radially from a center of the second electrode member 17 toward a second outer circumferential surface 26 of the second electrode member 17.

The number of the fluid supplying passages 23, formed at the second electrode member 17, and the number of the fluid discharging passages 24, formed at the second electrode member 17, are the same. Further, each of the fluid supplying passages 23 is formed into a substantially circular shape when seen in a cross-sectional view while each of the fluid discharging passages 24 is formed into a substantially rectangular shape when seen in a cross-sectional view, and thereby a cross-sectional area of each of the fluid discharging passages 24 is set to be larger than a cross-sectional area of each of the fluid supplying passages 23.

A circumferential groove 25 is formed at the second electrode member 17 so as to open toward a lower side of the second electrode member 17. The circumferential groove 25 communicates with an upstream side of the fluid supplying passages 23. A downstream side of the fluid discharging passages 24 opens toward a second outer circumferential surface 26 of the second electrode member 17 so that the electrolytic solution naturally flows from the fluid discharging passages 24 down to the electrolytic solution container 1.

The fixed plate 19, formed into a substantially annular-plate shape, includes a circular-shaped recessed surface portion 27 at a central portion thereof. The circular-shaped recessed surface portion 27 is coaxially provided with the piston insertion hole 20, and a diameter of the circular-shaped recessed surface portion 27 is substantially the same as a diameter of the piston insertion hole 20. A circular-shaped protruding surface portion 28 is coaxially formed at a central portion of the circular-shaped recessed surface portion 27. The circular-shaped protruding surface portion 28 supports an end surface of the piston A in a state where the axis of the piston A extends in the upper-lower direction.

A connecting fluid passage 29 is formed at the fixed plate 19. The connecting fluid passage 29 is connected to the supplying passage 7. Further, the connecting fluid passage 29 opens toward an upper surface of the fixed plate 19 so as to be in communication with the circumferential groove 25 of the second electrode member 17.

The movable plate 18 is formed with a circular-shaped through-hole 30, which is coaxially provided with the piston insertion hole 20 and whose diameter is substantially the same as the piston insertion hole 20, and thereby the movable plate 18 is formed into a substantially annular shape having a substantially rectangular-shaped cross section.

The piston A is held by the holding means (the first electrode member) 15 so that the piston A for processing is electrically connected to the anode terminal 4 a in a state where the axis of the piston A extends in the vertical direction. The piston A is inserted through the circular-shaped through-hole 30 of the movable plate 18 and through the piston insertion hole 20 of the second electrode member 17. The piston A is provided on the circular-shaped protruding surface portion 28 so that the lower end surface of the piston A contacts the circular-shaped protruding surface portion 28. Consequently, the piston A is coaxially positioned with the circular-shaped through-hole 30, the piston insertion hole 20 and an inner circumferential surface of the circular-shaped recessed surface portion 27 so as to include a predetermined interval for an entire circumference between the first outer circumferential surface 22 of the piston A and each of the circular-shaped through-hole 30, the piston insertion hole 20 and the inner circumferential surface of the circular-shaped recessed surface portion 27.

Elastic seal members 31 are respectively provided between the second electrode member 17 and the movable plate 18 and between the second electrode member 17 and the fixed plate 19. The elastic seal members 31 are respectively provided at both sides of the first piston ring groove A1 in a width direction thereof so as to seal a clearance B generated between the first outer circumferential surface 22 of the piston A and the inner circumferential surface 21 of the piston insertion hole 20.

More specifically, the elastic seal members 31 are respectively arranged at a first stepped portion 32 and a second stepped portion 33. The first stepped portion 32 is formed at a lower circumferential corner portion of the movable plate 18, which surrounds the circular-shaped through-hole 30, so as to face an upper surface of the second electrode member 17. The second stepped portion 33 is formed at a circumferential corner portion of the fixed plate 19, which surrounds the circular-shaped recessed circumferential portion 27, so as to face a lower surface of the second electrode member 17.

Each of the elastic seal members 31 is configured by a substantially annular-shaped elastic O ring, which is made of a nonconductive material (insulator), such as rubber and the like, and which includes a circular-shaped cross-section. A depth D of each of the first and second stepped portion 32 and 33 is set to be smaller than a diameter of each of the elastic seal members 31.

A thrusting mechanism 34 thrusts the elastic seal members 31 relative to the second electrode member 17 in the width direction of the first piston ring groove A1 so that the elastic seal members 31 protrude toward the outer circumferential surface 22 of the piston A, and thereby the elastic seal members 31 are elastically deformed so as to seal the clearance B generated between the outer circumferential surface 22 of the piston A and the inner circumferential surface 21 of the piston insertion hole 20. The thrusting mechanism 34 is switchable between a thrusting state for thrusting the elastic seal members 31 and a released state for releasing the thrusting of the elastic seal members 31.

The thrusting mechanism 34 includes a guide, a plurality of first compression springs 35, a plurality of second compression springs 36 and a thrusting member. The guide guides the second electrode member 17 and the movable plate 18 so that each of the second electrode member 17 and the movable plate 18 is movable in the upper-lower direction. The plurality of first compression springs 35 bias the second electrode member 17 and the movable plate 18 so that the second electrode member 17 and the movable plate 18 are spaced away from each other in the upper-lower direction. The plurality of second compression springs 36 bias the second electrode member 17 and the fixed plate 19 so that the second electrode member 17 and the fixed plate 19 are spaced away from each other in the upper-lower direction. The thrusting member thrusts the movable plate 18 toward the fixed plate 19 against a spring force of the first and second compression springs 35 and 36.

Before and after anodizing, as illustrated in FIG. 2, in the released state where the thrusting mechanism 34 releases the thrusting of the elastic seal members 31, the clearance B is generated between the outer circumferential surface 22 of the piston A and the inner circumferential surface 21 of the piton insertion hole 20. Therefore, the piston A may easily be attached/detached.

At the time of anodizing, as illustrated in FIG. 3, in the thrusting state where the thrusting mechanism 34 thrusts the elastic seal members 31, the clearance B, generated between the outer circumferential surface 22 of the piston A and the inner circumferential surface 21 of the piston insertion hole 20, is sealed by means of the elastic seal members 31, respectively provided at upper and lower sides of the first piston ring groove A1, thereby an annular spaced portion 37 is generated at a portion, which is sealed by the elastic seal members 31, and where the inner circumferential surface 21 of the piston insertion hole 20 faces the first piston ring groove A1 for an entire circumference so as to include a predetermined clearance therebetween.

Each of the elastic seal members 31 are relative to the second electrode member 17 in the width direction of the first piston ring groove A1 so that each of the elastic seal members 31 protrude toward the outer circumferential surface 22 of the piston A, and thereby the clearance B is sealed. Therefore, the annular spaced portion 37 is generated without covering the inner circumferential surface 21 by means of the elastic seal members 31. Consequently, an entire circumferential surface of the inner circumferential surface 21 may be utilized in order to energize the piston A and the second electrode member 17.

Accordingly, the second electrode member 17 is downsized. When the second electrode member 17 is made of a noble metal, such as platinum for example, a less amount of noble metal material may be required, and therefore a cost may be reduced.

Each of the plurality of fluid supplying passages 23 and each of the plurality of fluid discharging passages 24 are formed so as to open at the inner circumferential surface 21 alternately in a circumferential direction so as to include the interval between the adjacent passages. Therefore, supplying of the electrolytic solution to the annular spaced portion 37 and discharging of the electrolytic solution from the annular spaced portion 37 are smoothly executed. Consequently, an amount of the electrolytic solution supplied to the annular spaced portion 37 per time unit and an amount of the electrolytic solution discharged from the annular spaced portion 37 per time unit are increased. Accordingly, a temperature of the electrolytic solution within the annular spaced portion 37 is less likely to increase.

The cross-sectional area of each of the fluid discharging passages 24 is set to be larger than the cross-sectional area of each of the fluid supplying passages 23. Therefore, a pressure increase of the electrolytic solution within the annular spaced portion 37 is restricted. Consequently, the supplying of the electrolytic solution to the annular spaced portion 37 and the discharging of the electrolytic solution from the annular spaced portion 37 are smoothly executed. Accordingly, accumulation of the electrolytic solution in the annular spaced portion 37 may be avoided and a temperature increase of the electrolytic solution within the annular spaced portion 37 may be avoided.

In a state where the elastic seal members 31 are thrust, the lower surface of the second electrode member 17 and the upper surface of the fixed plate 19 contact each other, and the connecting fluid passage 29 communicates with the circumferential groove 25 of the second electrode member 17.

The supplying control portion 9 controls the operation of the supplying pump 8 so that the electrolytic solution is supplied to the oxidizing portion 3 when thrusting of the elastic seal members 31 by means of the thrusting mechanism 34 is detected, and so that the supplying of the electrolytic solution to the oxidizing portion 3 is canceled when a release of the thrusting of the elastic seal members 31 by means of the thrusting mechanism 34 is detected.

When the thrusting mechanism 34 starts to thrust the elastic seal members 31, air remains at the annular spaced portion 37. However, while the supplying of the electrolytic solution to the annular spaced portion 37 is being started, the remaining air is removed through the fluid discharging passages 24, and the removed air is then substituted in the electrolytic solution.

According to the above-described anodizing, the air remaining within the annular spaced portion 37 is substituted in the electrolytic solution, and then the electrolytic solution is supplied from the fluid supplying passages 23 to the annular spaced portion 37 while discharging the electrolytic solution within the annular spaced portion 37 from the fluid discharging passages 24 to the electrolytic solution container 1. Thus, the piston A and the second electrode member 17 are energized via the electrolytic solution, filled in the annular spaced portion 37, so that a surface of the first piston ring groove A1 is oxidized, and an alumite coating, whose thickness is even, is formed along a longitudinal direction (a circumferential direction) of the first piston ring groove A1. The electrolytic solution flows substantially horizontally through the fluid supplying passages 23, the annular spaced portion 37 and the fluid discharging passages 24.

Other Embodiment

The anodizing apparatus according to the embodiment may include a thrusting mechanism, which is configured to be manually operated so as to switch the thrusting state for thrusting the elastic seal members 31 and the released state for releasing the thrusting of the elastic seal members 31.

The anodizing apparatus according to the embodiment may be adapted not only for anodizing but also for surface processing, such as plating, in which a processing subject is immersed in a processing liquid and is applied with electric current.

Accordingly, a clearance B between the annular-shaped inner circumferential surface 21, formed at the second electrode member 17, and the first piston ring groove A1, formed at the first outer circumferential surface 22 of the piston A is sealed by means of the annular-shaped non-conductive elastic seal members 31 at both sides of the first piston ring groove A1 in the width direction thereof. Consequently, the annular spaced portion 37, which is sealed by the elastic seal members 31, is generated at a portion where the inner circumferential surface 21 of the second electrode member 17 faces the first piston ring groove A1 of the piston A so as to include the predetermined interval therebetween. The annular spaced portion 37 is sealed by the elastic seal members 31, which are thrust relative to the second electrode member 17 in the width direction of the first piston ring groove A1 by means of the thrusting mechanism 34 so as to be elastically deformed. The inner circumferential surface 21, formed at the second electrode member 17, is not covered by the elastic seal members 31. Therefore, the entire circumferential surface of the inner circumferential surface 21 may be utilized in order to energize the piston A and the second electrode member 17. Accordingly, a size of the second electrode member 17 may be reduced. The electrolytic solution is supplied from the fluid supplying passage 23, formed so as to open at the inner circumferential surface 21 of the second electrode member 17, to the annular spaced portion 37, and then the electrolytic solution, supplied to the annular spaced portion 37, is discharged from the fluid discharging passage 24, formed so as to open at the inner circumferential surface 21 of the second electrode member 17. At that time, the piston A and the second electrode member 17 are energized via the electrolytic solution, filled in the annular spaced portion 37, and thereby the surface of the first piston ring groove A1 is oxidized so as to form the coating. The annular-shaped inner circumferential surface 21 of the second electrode member 17 faces the first piston ring groove A1 of the piston A via the annular spaced portion 37. Therefore, density of an electric current may easily be uniformed along the first piston ring groove A1, and a coating, whose thickness is even along the longitudinal direction of the first piston ring groove A1, may easily be formed. Further, the thrusting mechanism 34 is switchable between the thrusting state for thrusting the elastic seal members 31 and the released state for releasing the thrusting of the elastic seal members 31. Therefore, when the thrusting mechanism 34 is switched to the released state for releasing thrusting of the elastic seal members 31, the piston A may easily be attached/detached. Accordingly, a plurality of processing subjects may be effectively processed.

The fluid supplying passage and the fluid discharging passage include a plurality of fluid supplying passages and a plurality of fluid discharging passages, respectively. Each of the plurality of fluid supplying passages and each of the plurality of fluid discharging passages are alternately arranged in a circumferential direction so as to include an interval therebetween. The plurality of fluid supplying passages and the plurality of fluid discharging passages are formed so as to open at the inner circumferential surface of the second electrode member.

When an electric current, having a high voltage, is applied in order to effectively form a coating in a short time, a temperature of the electrolytic solution within the annular spaced portion 37 may easily increase and a dielectric breakdown (burning) of the coating may occur. However, according to the configuration of the embodiment, each of the plurality of fluid supplying passages 23 and each of the plurality of fluid discharging passages 24 are formed so as to open at the inner circumferential surface 21 alternately in a circumferential direction so as to include the interval between the adjacent passages. Therefore, supplying of the electrolytic solution to the annular spaced portion 37 and discharging of the electrolytic solution from the annular spaced portion 37 are smoothly executed. Consequently, an amount of the electrolytic solution supplied to the annular spaced portion 37 per time unit and an amount of the electrolytic solution discharged from the annular spaced portion 37 per time unit are increased. Accordingly, a temperature of the electrolytic solution within the annular spaced portion 37 is less likely to increase. Since the electrolytic solution is effectively cooled, even when the electric current, having a high voltage is applied, the dielectric breakdown of the coating is less likely to occur. Accordingly, the coating whose thickness is even along the longitudinal direction of the first circumferential groove A1, may be effectively formed in a short time.

The cross-sectional area of the fluid discharging passage is set to be larger than a cross-sectional area of the fluid supplying passage.

When an electric current, having a high voltage, is applied in order to effectively form a coating in a short time, a temperature of the electrolytic solution within the annular spaced portion 37 may easily increase and a dielectric breakdown (burning) of the coating may occur. However, according to the configuration of the embodiment, the cross-sectional area of each of the fluid discharging passages 24 is set to be larger than the cross-sectional area of each of the fluid supplying passages 23. Therefore, a pressure increase of the electrolytic solution within the annular spaced portion 37 is restricted. Consequently, the supplying of the electrolytic solution to the annular spaced portion 37 and the discharging of the electrolytic solution from the annular spaced portion 37 are smoothly executed. Accordingly, accumulation of the electrolytic solution in the annular spaced portion 37 may be avoided and a temperature increase of the electrolytic solution within the annular spaced portion 37 may be avoided. Since the electrolytic solution is effectively cooled, even when the electric current, having a high voltage is applied, the dielectric breakdown of the coating is less likely to occur. Accordingly, the coating whose thickness is even along the longitudinal direction of the first circumferential groove A1, may be effectively formed in a short time.

The fluid supplying passage and the fluid discharging passage are formed at the second electrode member.

Accordingly, the second electrode member 17 is utilized in order to form the fluid supplying passage 23 and the fluid discharging passage 24. Therefore, an anodizing apparatus may be downsized.

The fluid supplying passage and the fluid discharging passage are arranged so as to extend radially outwardly from a center of the second electrode member toward an outer circumferential surface of the second electrode member.

The principles, preferred embodiment and mode of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims, be embraced thereby. 

1. An anodizing apparatus comprising: a first electrode member electrically connected to a processing subject, made of metal and formed with a circumferential groove at an outer circumferential surface thereof; a second electrode member including an inner circumferential surface, formed into an annular shape and facing each of the outer circumferential surface of the processing subject and the circumferential groove of the processing subject so as to include an interval between the second electrode member and each of the outer circumferential surface of the processing subject and the circumferential groove of the processing subject; elastic seal members being nonconductive, respectively formed into an annular shape, and respectively provided at both sides of the circumferential groove in a width direction thereof for sealing a clearance generated between the outer circumferential surface of the processing subject and the inner circumferential surface of the second electrode member; and a thrusting mechanism thrusting each of the elastic seal members relative to the second electrode member in the width direction of the circumferential groove of the processing subject, and thereby elastically deforming each of the elastic seal members so as to seal the clearance, wherein the thrusting mechanism is switchable between a thrusting state for thrusting the elastic seal members and a released state for releasing the thrusting of the elastic seal members, and wherein a fluid supplying passage, through which an electrolytic solution is supplied to the circumferential groove of the processing subject, and a fluid discharging passage, through which the electrolytic solution, supplied to the circumferential groove of the processing subject, is discharged, are formed so as to open at the inner circumferential surface of the second electrode member.
 2. The anodizing apparatus according to claim 1, wherein the fluid supplying passage and the fluid discharging passage include a plurality of fluid supplying passages and a plurality of fluid discharging passages, respectively, each of the plurality of fluid supplying passages and each of the plurality of fluid discharging passages are alternately arranged in a circumferential direction so as to include an interval therebetween, and wherein the plurality of fluid supplying passages and the plurality of fluid discharging passages are formed so as to open at the inner circumferential surface of the second electrode member.
 3. The anodizing apparatus according to claim 1, wherein the cross-sectional area of the fluid discharging passage is set to be larger than a cross-sectional area of the fluid supplying passage.
 4. The anodizing apparatus according to claim 2, wherein the cross-sectional area of the fluid discharging passage is set to be larger than a cross-sectional area of the fluid supplying passage.
 5. The anodizing apparatus according to claim 1, wherein the fluid supplying passage and the fluid discharging passage are formed at the second electrode member.
 6. The anodizing apparatus according to claim 2 wherein the fluid supplying passage and the fluid discharging passage are formed at the second electrode member.
 7. The anodizing apparatus according to claim 3, wherein the fluid supplying passage and the fluid discharging passage are formed at the second electrode member.
 8. The anodizing apparatus according to claim 4, wherein the fluid supplying passage and the fluid discharging passage are formed at the second electrode member.
 9. The anodizing apparatus according to claim 2, wherein the fluid supplying passage and the fluid discharging passage are arranged so as to extend radially outwardly from a center of the second electrode member toward an outer circumferential surface of the second electrode member. 